PHARMACOKINETICS:
Losartan is readily absorbed from the gastro-intestinal tract following oral administration, with an oral bioavailability of about 33%. It undergoes first-pass metabolism to form an active carboxylic acid metabolite E-3174(EXP-3174), which has greater pharmacological activity than losartan, and some inactive metabolites. Metabolism is primarily by cytochrome P450 isoenzymes CYP2C9 and CYp3A4. Peak plasma concentrations of losartan and E-3174 occur about 1 hour and 3 to 4 hours, respectively, after an oral dose. Both losartan and E-3174 are more than 98% bound to plasma proteins. Losartan is excreted in the urine and in the faeces via bile, as unchanged drug and metabolites. Following oral dosing about 35% of the dose is excreted in the urine and about 60% in the faeces. The terminal elimination half-lives of losartan and E-3174 are about 1.5 to 2.5 hours and 3 to 9 hours, respectively.
INDICATIONS:
Losartan is used in the management of hypertension and may have a role in patients who are unable to tolerate ACE inhibitors. It has also been tried in heart failure and in myocardial infarction.
DOSAGE AND ADMINISTRATION:
In hypertension the usual initial dose is 50 mg once daily. The maximum effect is achieved in about 3 to 6 weeks after initiating treatment. The dose may be increased, if necessary, to 100 mg once daily or in two divided doses as directed by the physician.
An initial dose of 25mg once daily may be used in the elderly over 75 years, and for patients for patients with moderate to severe renal impairment (creatinine clearance less than 20mL per minute), or intravascular fluid retention. A reduced dose should also be considered for patients with hepatic impairment.
CONTRAINDICATION:
Losartan is contraindicated in patients with are hypersensitive to any component of this product. Losartan is also contraindicated in pregnancy and if pregnancy is detected, losartan should be discontinued immediately.
ADVERSE EFFECTS:
Adverse effects of losartan have been reported to be usually mild and transient, and include dizziness and dose related orthostatic hypotension. Hypotension may occur particularly in patient with volume depletion (for example those who have received high-dose diuretics).
Impaired renal function and rarely, rash, angioedema, and raised alanine aminotransferase may occur. Hyperkalaemia and myalgia have been reported. Losartan appears less likely than ACE inhibitors to cause cough.
PRECAUTIONS:
Losartan is contra-indicated in pregnancy and breast feeding. It should also be used with caution in patients with renal artery stenosis. Reduced doses may be required in patients with hepatic impairment. Patients with volume depletion (for example those who have received high-dose diuretic therapy) may experience hypotension, which may be minimised by initiating treatment with a low dose of losartan.
Since hyperkalemia may occur, serum-potassium concentrations should be monitored, especially in the elderly and patients with renal impairment, and the concomitant use of potassium-spring diuretics should be avoided.
AVAILABILITY:
In a blister pack of 5x10 tablets.
WARNING ON TARTRAZINE:
This product contains FD & C yellow # 5 (Tartazine) which may cause allergic reactions to susceptible persons.
CAUTION :
Foods, Drugs, Devices, and Cosmetics Act prohibits dispensing without presc ription.
STORE AT TEMPERATURES NOT EXCEEDING 30° C.
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